THAT MAKES for an interesting tale, but is there any truth to it?

No, say historians. More likely the Red Hand of Ulster has its origins in a Biblical reference to the right hand being symbolic of God's power and authority. Interestingly, the Ripley cartoon shows Heremon O'Neil throwing his right hand ashore, though the legend usually says O'Neill cut off his left hand. Ripley's version fits the coat of arms that displays a right hand.

The Red Hand of Ulster may be traced to Psalm 98:1

O Sing unto the Lord a new song;
For he hath done marvellous things:
His right hand and his holy arm,
Hath gotten him the Victory

Also, The Children of Israel in their passage through the Red Sea gave the power and glory for their deliverance to the Right Hand of God (Exodus 15:6):

Thy Right Hand, O Lord, is become Glorious
In power : Thy Right Hand, O Lord, hath
Dashed in pieces the enemy.

We prefer the bloody hand legend. Maybe Hollywood will turn it into a movie, undoubtedly starring Johnny Depp (who'll insist on really cutting off his right hand).